Optical pickup device, and recorder and/or player

ABSTRACT

An optical pickup device includes a feed screw to move an optical pickup having an objective lens radially on an optical disc, a sliding member provided for slidable movement in relation to the optical pickup, and connected to the optical pickup by a coil spring that forces a shutter in a direction of unmasking the objective lens, and a connection member that connects the feed screw and sliding member to each other. As the feed screw is rotated, the sliding member moves the optical pickup radially on the optical disc, and when the optical pickup has arrived at a position at the lead-in side of the optical disc, the sliding member is further slid against the force of the coil spring to move the shutter and mask the objective lens.

TECHNICAL FIELD

The present invention relates to an optical pickup device which recordsor reads information signals to or from an optical disc, magneto-opticaldisc or the like, and also to a recorder and/or player incorporating theoptical pickup device.

BACKGROUND ART

Some of the conventional optical pickup devices incorporated in theoptical disc recorders and/or players are provided with a dust-prooffeature to prevent any foreign matter such as dust from adhering to theobjective lens.

For example, the optical pickup device with such a dust-proof featureincludes an optical pickup mounted on a base to be movable radially ofan optical disc, and a moving mechanism to move the optical pickupradially of the optical disc. The optical pickup device also includes acompartment for housing the optical pickup as a whole. In this opticalpickup device, when the recorder and/or player is not in use, the movingmechanism is controlled to house the optical pickup into the compartmentin order to prevent any foreign matter such as dust from adhering to theobjective lens in the optical pickup.

In such a dust-proof feature to house the entire optical pickup in thecompartment when the recorder and/or player is not in use, however, thecompartment has to be larger in dimensions than the optical pickup,which will require the optical pickup device to have an increased size.Namely, a small optical pickup device cannot use any such dust-prooffeature.

Also, since the dust-proof feature is intended primarily for preventionof any foreign matter from adhering to the objective lens, it shouldonly be capable of masking the objective lens without having to housethe entire optical pickup.

Also, the recent optical disc as a recording medium can recordinformation signals mode densely. Accordingly, the recent optical pickupuses an objective lens having a larger numerical aperture and thus thedistance between the optical disc and objective lens is shorter.Therefore, when the optical disc is moved into or from inside thecompartment, the objective lens will possibly touch with the innersurface of the compartment and be scratched. Once the objective lens isthus scratched, information signals cannot accurately be read from orwritten to the optical disc.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention has an object to overcome theabovementioned drawbacks of the related art by providing an opticalpickup device whose entirety can be made smaller by simplification ofthe dust-proof feature, and also to a recorder and/or playerincorporating the optical pickup device.

The present invention has another object to provide an optical pickupdevice designed to prevent the objective lens from being scratched whenthe objective lens is closed by a shutter in order to prevent anyforeign matter such as dust from adhering to the objective lens, and arecorder and/or player incorporating the optical pickup device.

The above object can be attained by providing an optical pickup deviceincluding according to the present invention:

an optical pickup supported to be movable along a linear guide providedon a base to extend radially of an optical disc, and having providedthereon an objective lens which focuses a light beam emitted from alight source onto the signal recording surface of the optical disc;

a feed screw provided along the moving direction of the optical pickupto move the optical pickup radially of the optical disc; and

a sliding member provided to be slidable radially of the optical disc inrelation to the optical pickup, connected to the feed screw with atransmission engaged on the feed screw, having provided thereon ashutter which masks the objective lens, and connected to the opticalpickup by a forcing piece which forces the shutter in a direction ofunmasking the objective lens;

as the feed screw with the transmission engaged thereon is rotated, thesliding member is moved along with the optical pickup radially of theoptical disc. When the sliding member has been moved to a play waitingposition, the optical pickup is limited by a limiter provided on thebase from moving. Then as the sliding member is slid against the forceof the forcing piece in relation to the optical pickup, the shuttermasks the objective lens.

Also the above object can be attained by providing a recorder and/orplayer including according to the present invention:

an optical pickup supported to be movable along a linear guide providedon a base to extend radially of an optical disc, and having providedthereon an objective lens which focuses a light beam emitted from alight source onto the signal recording surface of the optical disc; and

a moving mechanism for moving the optical pickup along the guide.

The moving mechanism includes:

a feed screw provided along the moving direction of the optical pickupto move the optical pickup radially of the optical disc; and

a sliding member provided to be slidable radially of the optical disc inrelation to the-optical pickup, connected to the feed screw with atransmission engaged on the feed screw, having provided thereon ashutter which masks the objective lens, and connected to the opticalpickup by a forcing piece which forces the shutter in a direction ofunmasking the objective lens;

as the feed screw with the transmission engaged thereon is rotated, thesliding member being moved along with the optical disc radially of theoptical disc. When the optical pickup has been moved to a play waitingposition, it is limited by a limiter provided on the base from moving.Then as the sliding member is slid against the force of the forcingpiece in relation to the optical pickup, the shutter masks the objectivelens.

Also the above object can be attained by providing an optical pickupdevice including according to the present invention:

an optical pickup having provided thereon an objective lens whichfocuses a light beam emitted from a light source on the signal recordingsurface of an optical disc; and

a shutter which masks the objective lens from outside; and

a movement control means for controlling the movement of the opticaldisc while supporting the objective lens to be movable optical-axiallyof the objective lens.

When masking the objective lens with the shutter, the movement controlmeans further moves the objective lens at a predetermined positionfurther away from the optical disc.

Also the above object can be attained by providing a recorder and/orplayer including according to the present invention:

an optical pickup having an objective lens which focuses a light beamemitted from a light source on the signal recording surface of anoptical disc;

a moving mechanism for moving the optical pickup along a guide providedon a base on which the optical pickup is mounted and radially of theoptical disc;

a shutter which masks the objective lens from outside; and

a movement control means for controlling the movement of the objectivelens while supporting the objective lens to be movable optical-axiallyof the objective lens.

When the optical pickup is moved by the moving mechanism to a playwaiting position at the lead-in or lead-out side of the optical disc tomask the objective lens with the shutter, the movement control meansmoves the objective lens at a predetermined position further away fromthe optical disc.

These objects and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription of the best mode for carrying out the present invention whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a disc drive unit.

FIG. 2 is an exploded perspective view of the disc drive unit.

FIG. 3 is a perspective view of an optical pickup moving mechanism in anembodiment of the optical pickup device according to the presentinvention.

FIG. 4 is a side elevation of a moving mechanism included in the opticalpickup device.

FIG. 5 explains the control of the moving mechanism.

FIG. 6 explains the operation of a drive motor which rotates the feedscrew for moving the optical pickup from the lead-out side to thelead-in side of an optical disc D.

FIG. 7 explains the positions of the objective lens for playing a CD.

FIG. 8 explains the positions of the objective lens for playing a DVD.

FIG. 9 explains the state of the moving mechanism with the optical discD being played.

FIG. 10 explains the state of the moving mechanism with the lead-in areaof the optical disc D being read.

FIG. 11 explains the state of the moving mechanism with the objectivelens masked with the shutter.

FIG. 12 is a side elevation of the moving mechanism with the shutterbeing in a position for masking the objective lens.

FIG. 13 explains the operation of the drive motor which rotates the feedscrew for moving the optical pickup from the lead-in to lead-out side ofthe optical disc.

FIG. 14 is an exploded perspective view of another embodiment of theoptical pickup device according to the present invention.

FIG. 15 is a perspective view explaining a support member included inthe optical pickup device.

FIG. 16 is a plan view explaining a rack of the support member and rackof the sliding member, included in the optical pickup device.

FIG. 17 is a plan view of a shutter mechanism included in the opticalpickup device with the shutter being opened.

FIG. 18 is a plan view of the shutter mechanism with the shutter beingclosed.

FIG. 19 is an exploded perspective view of still another embodiment ofthe optical pickup device according to the present invention.

FIG. 20 is a perspective view of the optical pickup device.

FIG. 21 is a plan view explaining a rack of a support base and rack ofthe sliding member, included in the optical pickup device.

FIG. 22 is a plan view explaining one tooth of the rack of the supportbase.

FIG. 23 schematically illustrates the optical pickup device with ashutter plate in the closed position.

FIG. 24 schematically illustrates the shutter plate in the openposition.

FIG. 25 schematically illustrates the optical pickup with the objectivelens being in the lead-in area of the optical disc.

FIG. 26 schematically illustrates the optical pickup with the objectivelens being in the recording area of the optical disc.

BEST MODE FOR CARRYING OUT THE INVENTION

The disc drive unit according to the present invention will be describedherebelow with reference to the accompanying drawings.

The disc drive unit according to the present invention is generallyindicated with a reference 1 in FIG. 1. The disc drive unit 1 isdirected for reading information signals from an optical disc indicatedwith a reference D, and more specifically, from a so-called compact disc(CD) and digital versatile disc (DVD). The optical disc D has recordedin a lead-in area (at the inner circumference side) thereof outside andaround the lead-in area TOC (table of contents) which is data formanagement of address information etc. indicative of data locationswhere the data are recorded, and in a program area thereof informationsignals such as video data, image data, audio data, computer program,processing data to be processed by a computer, etc. A lead-out area isprovided outside and around the program area. An optical pickup providedin the disc drive unit 1 reads the information signals recorded in eachrecording area while being moved from the inner to outer circumferenceof the optical disc D.

The above disc drive unit 1 includes an optical pickup mechanism 2 towrite and read information to and from the optical disc D, and a discdrive mechanism 3 to rotate the optical disc D.

The optical pickup mechanism 2 includes an optical pickup 11 to readinformation signals from the optical disc D, a moving mechanism 12 tomove the optical pickup 11 radially of the optical disc D, and a base 13having the optical pickup 11 mounted thereon to be movable radially ofthe optical disc D.

As shown in FIGS. 1 and 2, the base 13 has formed therein an opening 16in which the optical pickup 11 is provided movably from the inner toouter circumference, or vice versa, of the optical disc D, that is, inthe directions of arrows A₁ and A₂ in FIGS. 1 and 2. The optical pickup11 consists an optical system block in which a light beam emitted from asemiconductor laser (light source) is focused by an objective lens 14 onthe signal recording surface of the optical disc D and a return lightfrom the signal recording surface of the optical disc D is detected by aphotodetector, and an objective lens driving block which moves theobjective lens 14 optical-axially of the latter (focusing direction) andin a direction orthogonal to the optical axis of the objective lens 14(tracking direction). These optical system block and objective lensdriving block are provided inside a cover 15.

The cover 15 is formed from a resin material such as ABS in the generalshape of a box whose main surface 15 a is generally parallel to thesignal recording surface of the optical disc D. As will be seen fromFIGS. 1 and 2, the cover 15 has formed nearly in the center of the mainsurface 15 a an opening 18 through which the objective lens 14 supportedby a lens holder can face directly the signal recording surface of theoptical disc D and also face outside. The opening 18 has a generallyelliptic shape of which the longer diameter extends radially of theoptical disc D. On the main surface 15 a of the cover 15, there isformed a projection 17 around the opening 18. The projection 17 ishigher than the top of the objective lens 14. Since the projection 17 isformed higher than the top of the objective lens 14, so a shutter whichwill be described in detail later will not touch the top of theobjective lens 14 when the shutter moves to mask or unmask the objectivelens 14. Therefore, the objective lens 14 will not be scratched by theshutter.

As shown in FIGS. 2 and 3, the moving mechanism 12 by which the opticalpickup 11 constructed as above is moved radially of the optical disc Dincludes a support member 21 to support the optical pickup 11, a feedscrew 22 to move the support member 21 having the optical pickup 11mounted thereon radially of the optical disc D, a guide 23 to guide thesupport member 21 when moving the support member 21 along with theoptical pickup 11 radially of the optical disc D, a sliding member 24,mounted on the support member 21 and connected to the feed screw 22, tomove the support member 21 radially of the optical disc D, and a coilspring 25 to connect the support member 21 and sliding member 24 to eachother.

As shown in FIGS. 2 and 3, the support member 21 has the optical pickup11 mounted on the main surface thereof. It has a through-hole 31 formedin a lower portion thereof and through which the feed screw 22 ispenetrated, and a pair of guide pieces 32 provided at the lateral sidethereof and engaged a guide 23 formed along a lateral edge, parallel tothe moving direction of the optical pickup 11, of the opening 16 formedin the base 13.

The feed screw 22 inserted in the through-hole 31 is an externallythreaded metal rod. It extends in the moving direction of the opticalpickup 11 and is supported rotatably in a support provided on the rearside of the base 13. As shown in FIGS. 1 and 2, the feed screw 22 hasprovided at one end thereof a gear 33 which is connected to a drivemotor 35 by a gear train 34 including a plurality of gears. The supportmember 21 has formed therein an opening 40 through which the feed screw22 through the through-hole 31 is exposed to outside at a middle portionthereof.

The guide pieces 32 in pair provided at the lateral side of the opticalpickup 11 are engaged on the guide 23 provided at the lateral edge ofthe opening 16 in the base 13. Namely, the guide 23 is laid between theguide pieces 32, and thus guides the support member 21 being moved inthe directions of arrows A₁ and A₂ in FIG. 2, namely, radially of theoptical disc D. It also holds the support member 21 to prevent theoptical pickup 11 from bumping when a vibration or the like is appliedin a direction orthogonal to the main surface of the base 13.

The support member 21 has provided at one end thereof nearer to theouter circumference of the optical disc D a retainer 36 to which thecoil spring 25 is hooked, and at the other end thereof nearer to theinner circumference of the optical disc D a guide piece 37 to guide thesliding member 24 being slid. It should be noted that the retainer 36also guides the sliding member 24 being slid.

As shown in FIGS. 2 and 3, the support member 21 has provided in aposition nearer to the inner circumference of the optical disc D astopper 38 to prevent the support member 21 from colliding against thedisc drive mechanism 3 due to having moved excessively in the directionof arrow A₁ in FIG. 2. The inner circumference-side stopper 38 isprojected from the lateral side of the support member 21 nearer to theinner circumference of the optical disc D. On the other hand, the base13 is cut (indicated at a reference 39) at the lateral edge, near thedisc drive mechanism 3, of the opening 16 in which the optical pickup 11is moved. When the support member 21 is moved toward the center of theoptical disc D, the inner circumference-side stopper 38 comes into thecut 39 and abuts the inner end of the cut 39 to limit the inwardmovement of the support member 21. Thus, the cut 39 will also be called“inward move limit cut 39”.

As shown in FIGS. 2 and 3, the support member 21 has also provided in aposition corresponding to the outer circumference of the optical disc Da stopper 41 to prevent the support member 21 from colliding against thedisc drive mechanism 2 due to having moved excessively in the directionof arrow A₂ in FIG. 2. On the other hand, the base 13 is cut (indicatedat a reference 42) at the lateral edge opposite to the lateral edge, inwhich the inward move limit cut 39 is formed, namely, nearer to theouter circumference of the optical disc D, of the opening 16 in whichthe optical pickup 11 is moved. When the support member 21 is moved awayfrom the center of the optical disc D, the outer-circumference stopper41 comes into the cut 42 and abuts the inner end of the latter to limitthe outward movement of the support member 21. The cut 42 will also becalled “outward move limit cut 42”. Thus, the optical pickup 11supported on the support member 21 is limited in disc-radial movementbetween the inner circumference-side stopper 38 arriving at the inwardmove limit cut 39 and the outer-circumference stopper 41 arriving at theoutward move limit cut 42.

As shown in FIGS. 2 and 3, the sliding member 24 mounted on the supportmember 21 is a generally rectangular plate having first and second guideholes 43 and 44 formed therein longitudinally thereof, namely, axiallyof the feed screw 22. These guide holes 43 and 44 guide the slidingmember 24 being slid. The retainer 36 of the support member 21 to whichthe coil spring 25 is hooked is engaged in the first guide hole 43. Thesliding member 24 has provided thereon at an end of the first guide hole43 in the direction of arrow A₂ in FIG. 2 a limiter 45 on which theretainer 36 engaged in the first guide hole 43 is put into abutment toprevent the sliding member 24 from sliding excessively toward the innercircumference of the optical disc D. In addition, the sliding member 24has provided thereon at the middle of and across the first guide hole 43a pair of projections 46 the retainer 36 engaged in the first guide hole43 abuts to prevent the sliding member 24 from moving excessively towardthe outer circumference of the optical disc D.

The second guide hole 44 has the guide piece 37 of the support member 21engaged therein and works along with the first guide hole 43 to limitthe movement of the sliding member 24. The coil spring 25 is hooked atthe other end thereof to the end of the second guide hole 44 in thedirection of arrow A₂ in FIG. 2. Thus, with the retainer 36 of thesupport member 21 being engaged in the first guide hole 43 and the guidepiece 37 being engaged in the second guide hole 44, the sliding member24 connected to the support member 21 by the coil spring 25 is normallyforced under the force of the coil spring 25 in the direction of arrowA₂ toward the outer circumference of the optical disc D while theprojections 46 are in abutment on one side of the retainer 36.

The sliding member 24 has provided thereon a shutter 47 which masks theobjective lens 14 provided in the opening 18 in the cover 15 of theoptical pickup. 11. As the sliding member 24 is slid, the shutter 47 ismoved to a position where it unmasks the objective lens 14 or to aposition where it masks the objective lens 14. That is, when playing theoptical disc D, the shutter 47 is moved in the direction of arrow A₂ inFIGS. 1 thru 3 to unmask the objective lens 14. Otherwise, the shutter47 is slid in the direction of arrow A₁ in FIGS. 1 thru 3 to mask theobjective lens 14. The shutter 47 is formed from a resin material suchas POM (polyoxymethylene) to have a generally rectangular shape and anarea large enough to mask the opening 18 in the cover 15 as shown inFIG. 2. As shown in FIG. 2, the shutter 47 is formed integrally with thesliding member 24 with a pair of linear, elastic coupling pieces 48 laidbetween them, and forced to over the cover 15 under the elasticity ofthe coupling pieces 48. It should be noted that the projection 17 isformed around the objective lens as previously mentioned and since theprojection 17 is formed higher than the top of the objective lens 14, sothe shutter 47 will not touch the top of the objective lens 14 but theprojection 17 when the shutter 47 is in the position of masking theobjective lens 14.

The sliding member 24 has a transmission 51 extending from above tounder the feed screw 22 in a wraparound relation to the latter as bestshown in FIGS. 2 and 4. The transmission 51 is engaged on the lower sideof the feed screw 22. The transmission 51 has formed at the free endthereof an engagement projection 52 engaged in the thread of the feedscrew 22 exposed to outside at the middle portion thereof through theopening 40 in the support member 21. The transmission 51 is formed froman elastic material such as a leaf spring. It is fixed to the slidingmember 24 to be movable along with the latter. The transmission 51 maybe formed integrally with the sliding member 24. The engagementprojection 52 of the transmission 51 is always in mesh with the threadof the feed screw 22 under the elasticity of the transmission 51 itself.Thus, as the feed screw 22 is rotated, the sliding member 24 havingmounted thereon the transmission 51 which converts a rotation of thefeed screw 22 into a linear motion is slid in the directions of arrowsA₁ and A₂ in FIGS. 1 thru 3 to move the shutter 47 to the position wherethe objective lens 14 is unmasked or to the position where the objectivelens 14 is masked.

As mentioned above, the coil spring 25 is hooked at one end thereof tothe retainer 36 of the support member 21 and at the other end to the endof the second guide hole 44. The coil spring 25 forces the slidingmember 24 in the direction of arrow A₂ in FIGS. 2 and 3 for the shutter47 to unmask the objective lens 14 and also connects the sliding member24 and support member 21 to each other. Therefore, when the slidingmember 24 is driven to slide in the directions of A₁ and A₂ in FIGS. 2and 3 as the feed screw 22 is rotated, the support member 21 having theoptical pickup 11 mounted thereon is correspondingly moved radially ofthe optical disc D. Thus, the coil spring 25 connecting the supportmember 21 and sliding member 24 to each other has such a force as not tocause the support member 21 having the optical pickup 11 mounted thereonto be misaligned with the sliding member 24 due to a quick movement ofthe optical pickup 11 for a jump from one track to another or the like.

Further, as shown in FIG. 2, the moving mechanism 12 includes adetection mechanism 53 to detect when the optical pickup 11 has beenmoved to the lead-in area of the optical disc D. The detection mechanism53 is composed of a detection switch or limit switch 54 fixed to thesupport member 21 and a switch counterpart 56 to push a sense piece 55of the detection switch 54.

The detection switch 54 is fixed to the support member 21 with the sensepiece 55 thereof directed toward the inner circumference of the opticaldisc D as shown in FIG. 2. The switch counterpart 56 is provided on thelateral edge, at the side of the disc rotation drive mechanism 3, of theopening 16 in which the optical pickup 11 is moved. More particularly,when the optical pickup 11 is moved nearly to the center of the lead-inarea for reading TOC on the optical disc D, the sense piece 55 of thedetection switch 54 is pressed to the switch counterpart 56, whereby itis detected that the optical pick 11 is located in a reading position inthe lead-in area of the optical disc D.

More particularly, a detection signal produced by the detection switch54 is supplied to a microcomputer 61 as shown in FIG. 5. Upon receptionof the detection signal, the microcomputer 61 will start counting apredetermined length of time by a timer 62 and supply, for the length oftime, a drive circuit 63 for a drive motor 35 with a drive signal whichdrives the drive motor 35 to rotate the feed screw 22. Thus, the drivemotor 35 continuously drives the feed screw 22 for the length of timethe microcomputer 61 counts. Since the support member 21 with theoptical pickup 11 mounted thereon is limited in position with the innercircumference-side stopper 38 abutting the inward move limit cut 39 inthe base 13, so the sliding member 24 will be moved in the direction ofarrow A₁ in FIG. 5 against the force of the coil spring 25 and hence theshutter 47 mask the objective lens 14.

For the shutter 47 to mask the objective lens 14, the microcomputer 61will apply a reverse bias voltage for moving the objective lens 14 awayfrom the optical disc D to a focusing drive 64 which controls focusingof the objective lens 14 for a predetermined period in order to preventthe objective lens 14 from touching the shutter 47. The focusing drive64 moves the objective lens 14 in the focusing direction under theaction of a magnetic field developed by a magnet and a current flowingthrough a focusing coil. Thus, the microcomputer 61 moves the objectivelens 14 in a direction further away from the optical disc D from aposition where the objective lens 14 stays when the apparatus is turnedoff.

As shown in FIGS. 1 and 5, the disc rotation drive mechanism 3 includesa spindle motor 66 to rotate the optical disc D. The spindle motor 66 isfixed to the base 13 and has provided on the drive shaft thereof a disctable included in the disc drive and on which the optical disc D is set.The spindle motor 66 drives to rotate the optical disc D set on the disctable at a constant linear velocity, for example.

The disc drive unit 1 constructed as above operates as will be describedbelow. First, at a time t1 in FIG. 6, the disc drive unit 1 is readinginformation signals recorded in the program area of the optical disc D.It should be noted here that the disc drive unit 1 is capable of playinga CD and DVD different in working distance from each other. For playinga CD, the focusing drive 64 moves the objective lens 14 from a referenceposition where no voltage is applied to the focusing drive 64 to anin-focus position nearer to the CD than a position where the objectivelens 14 focuses a light beam on the signal recording surface, as shownin FIGS. 5 and 7. Also, the focusing drive 64 is designed to move, whenthe CD incurs a side-runout or the like, the objective lens 14 to afocusing control position nearer to the CD than the in-focus positionwhere focusing is controlled. That is, for playing a CD, the focusingdrive 64 can focus the objective lens 14 while following such aside-runout of the disc by moving the objective lens 14 to the in-focusposition or to the focusing control position.

Also, there is provided a tracking controller 65 composed of a trackingcoil and magnet to move the objective lens 14 in the tracking directionunder the action of a current supplied to the tracking coil and amagnetic field developed. When a CD is being played, the trackingcontroller 65 controls tracking of the objective lens 14 by moving theobjective lens 14 in the tracking direction included in a planeorthogonal to the optical axis of the objective lens 14.

Also, for playing a DVD, the focusing drive 64 moves the objective lens14 from the reference position where no voltage is applied to thefocusing drive 64 and also the objective lens 14 focuses a light beam onthe signal recording surface to the focusing control position nearer tothe DVD than the in-focus position where focusing control is to be madewhen the DVD incurs a side-runout., as shown in FIGS. 5 and 8. That is,for playing a DVD, the focusing drive 64 can focus the objective lens 14while following such a side-runout of the disc by moving the objectivelens 14 from the reference position to the focusing control position.

When a DVD is being played, the tracking controller 65 controls trackingof the objective lens 14 by moving the objective lens 14 in the trackingdirection included in a plane orthogonal to the optical axis of theobjective lens 14.

Thus, a return light from the signal recording surface of a CD or DVD isdetected and converted into an electricity by the photodetector providedin the optical system block of the optical pickup 11.

As mentioned above, when the optical pickup 11 plays a CD or DVD, thesliding member 24 has been slid in the direction of arrow A₂ in FIG. 9under the force of the coil spring 25 in relation to the support member21 with the projections 46 being in abutment on the retainer 36 as shownin FIG. 9. Therefore, also the shutter 47 to mask the objective lens 14is in the position where the objective lens 14 is unmasked, and thus alight beam can be projected to the signal recording surface of theoptical disc D. As information signals recorded in the program area ofthe optical disc D are read, the drive motor 35 rotates the feed screw22 and the optical pickup 11 mounted on the support member 21 iscorrespondingly moved along with the sliding member 24 in the directionsof arrows A₁ and A₂ in FIG. 9 (radially of the optical disc D). In theoptical pickup 11, the objective lens 14 focuses a light beam emittedfrom the light source, and the photodetector detects a return light fromthe signal recording surface of the optical disc D and reads theinformation signals. At this time, since the coil spring 25 has such aforce as not to cause the support member 21 with the optical pickup 11mounted thereon to be displaced in relation to the sliding member 24when the optical pickup 11 is quickly moved for a track jump or thelike, the optical pickup 11 mounted on the support member 21 can beprevented from being misaligned with the sliding member 24 which is sliddirectly by the feed screw 22. It should be noted that when the opticalpickup 11 is moved to the outer circumference, that is, to the lead-outarea, of the optical disc D, the outer-circumference stopper 41 is putinto abutment on the inner end of the outward move limit cut 42, therebypermitting to prevent the optical pickup 11 from moving excessively tothe outer circumference of the optical disc D.

Next, when the optical pickup 11 is moved from the inner to outercircumference, namely, to the lead-in area, of the optical disc D forending the disc playing at a time t2 in FIG. 6, the innercircumference-side stopper 38 provided on the support member 21 abutsthe inner end of the inward move limit cut 39 formed in the base 13 asshown in FIG. 10, thereby limiting the support member 21 having theoptical pickup 11 mounted thereon from moving further to the innercircumference of the optical disc D. At the same time, the sense piece55 of the detection switch 54 provided on the support member 21 ispressed by the switch counterpart 56 provided on the base 13 and thusthe detection switch 54 is turned on to supply a detection signal to themicrocomputer 61.

Upon reception of the detection signal from the detection switch 54, themicroprocessor 61 will start counting a predetermined length of timeuntil the shutter 47 provided on the sliding member 24 is moved to theposition where it masks the objective lens 14. The innercircumference-side stopper 38 abuts the inner end of the inward move cut39 and thus support member 21 cannot move in the direction of arrow A₁in FIG. 10. As the drive motor 35 continuously drives the feed screw 22to further rotate, the sliding member 24 will be moved against the forceof the coil spring 25 in the direction of arrow A₁ in FI. 10. Thus, theshutter 47 provided on the sliding member 24 starts, at a time t3 inFIG. 6, moving toward the position where it will mask the objective lens14.

Upon elapse of the predetermined length of time, the microprocessor 61stops, at a time t4 in FIG. 6, the drive motor 35 from running. Then theshutter 47 is moved to the position where it masks the objective lens14, as shown in FIGS. 11 and 12 and will mask the objective lens 14. Atthis time, since the shutter 47 is forced by the coupling pieces 48toward the objective lens 14, it is possible to prevent dust or the likefrom entering through any clearance and adhering to the objective lens14. Thus, while the disc drive unit 1 is not in use, it is possible toprevent any foreign matter such as dust from adhering to the objectivelens 14. It should be noted that since the limiter 45 abuts the otherside of the retainer 36 of the support member 21, the sliding member 24is mechanically limited from being moved.

As shown in FIG. 6, the microcomputer 61 will apply a reverse biasvoltage to the focusing drive 64 for the predetermined period after thedetection switch 54 is turned on at the time t2 in FIG. 6 until the timet4. Thus, the focusing drive 64 moves the objective lens 14 to a parkingposition, inside the cover 15, farthest from the optical disc D as shownin FIGS. 7 and 8. Therefore, it is possible to prevent the shutter 47from touching and scratching the objective lens 14 when being moved fromthe position where it unmasks the objective lens 14 to the positionwhere it masks the objective lens 14. At the time t4 when thepredetermined length of time has elapsed, the microcomputer 61 willapply no voltage or apply 0 V, for example, to the focusing drive 64.Thus, the objective lens 14 is moved from the parking position back tothe reference position as shown in FIGS. 7 and 8. In the referenceposition, the top of the objective lens 14 is lower than the top of theprojection 17. Therefore, it is possible to prevent the shutter 47 fromtouching and scratching the objective lens 14. It should be noted thatshould the objective lens 14 touch the shutter 47 due to a vibration orthe like, the touch is just a point contact and so the scratching of theobjective lens 14 can be minimized.

Next, the operations to start playing an optical disc D will bedescribed with reference to FIG. 13. When a play start signal or thelike is supplied to the microcomputer 61, the latter will detect, at atime t5, that the detection switch 54 is on and the optical pickup 11 isin a lead-in read position at the innermost circumference of the opticaldisc D. At the same time, the microcomputer 61 applies a reverse biasvoltage to the focusing drive 64 to move the objective lens 14 from thereference position in FIGS. 7 and 8 to the parking position to preventthe shutter 47 from touching the objective lens 14 when the shutter 47moves from the position where it masks the objective lens 14 to theunmasking position. Next, at a time t6, the microcomputer 61 turns onthe drive motor 35 to rotate the feed screw 22. Thus, the sliding member24 connected to the feed screw 22 by the transmission 51 will startmoving in the direction of arrow A₂ in FIG. 11. That is, the shutter 47mounted on the sliding member 24 starts moving from the position whereit masks the objective lens 14 to the unmasking position.

When the sliding member 24 has moved in the direction of arrow A₂ inFIG. 11 and the shutter 47 has moved to the position where it unmasksthe objective lens 14, the detection switch 54 is turned off at a timet7 as shown in FIG. 10. Detecting that the detection switch 54 is off,the microcomputer 61 will pull in the objective lens 14 so that theoptical pickup 11 can read information signals, particularly, TOC,recorded in the lead-in area of the optical disc D. That is, thefocusing drive 64 is applied with a reverse bias voltage and biasvoltage. Thus, the objective lens 14 is moved to the focusing controlposition, parking position and then to the in-focus position as shown inFIGS. 7 and 8. Thereafter, the moving mechanism 12 will be ready asshown in FIG. 9 for reading the information signals recorded in theoptical disc D. At this time, the optical pickup 11 is located nearly inthe center of the lead-in area of the optical disc D, and hence TOC canreadily be read without having to make any operations for moving theoptical pickup 11.

The disc drive unit 1 having been described so far needs no compartmentfor housing the optical pickup 11 when not in use as in the conventionaldisc drive units in order to prevent any foreign matter such as dustfrom adhering to the objective lens 14 of the optical pickup 11. In theaforementioned disc drive unit 1 according to the present invention, theshutter 47 is moved by the feed screw 22 which moves the optical pickup11 radially of the optical disc D to mask or unmask the objective lens14, whereby it is possible to design the optical pickup 11 compact andsimple and prevent any foreign matter such as dust from adhering to theobjective lens 14. Also, the disc drive unit 1 can use the feed screw22, such as used in many small portable devices, in the moving mechanism12 which feeds the optical pickup 11 radially of the optical disc D andalso the shutter 47 which prevents any foreign matter such as dust fromadhering to the objective lens 14. Since the objective lens 14 is movedaway from the optical disc D when moving the shutter 47 to mask orunmask the objective lens 14, it is possible to prevent the shutter 47from touching and scratching the objective lens 14.

Note here that the reverse bias voltage may be applied to the focusingdrive 64 only when the objective lens 14 is masked or unmasked by theshutter 47 and the objective lens 14 may be pulled in to the parkingposition as in an optical pickup mechanism which will be describedherebelow.

Referring now to FIG. 14, there is illustrated in the form of anexploded perspective view another embodiment of the optical pickupdevice according to the present invention. This optical pickup device ormechanism is generally indicated with a reference 110. As shown in FIG.14, the optical pickup mechanism 110 includes an optical pickup 111 toread information from an optical disc D, a moving mechanism 112 to movethe optical pickup 111 radially of the optical disc D, and a base 113 tosupport the optical pickup 111 movably and also the moving mechanism112.

As shown in FIG. 14, the optical pickup 111 is provided movably in thedirections of arrows B₁ and B₂ in FIG. 14 in an opening 116 formed inthe base 113. The optical pickup 111 has an optical system (not shown)including an objective lens 118, a drive unit (not shown) which movesthe objective lens 118 optical-axially of the latter and in a directionorthogonal to the optical axis, and a cover 120 to cover the drive unit.

The optical system includes a light source to emit a laser light, agroup of lenses forming together an optical path, and a photodetector todetect a return light from the optical disc D (which are not shown).Also, the drive unit includes a lens holder to hole the objective lens118, a support mechanism to support the lens holder movably, and anelectromagnetic circuit to drive the lens holder electromagnetically(which are not shown). The cover 120 is formed from a resin material,for example, to have a nearly box-like shape, as shown in FIG. 14 andhas formed therein a generally rectangular opening 121 through which theoptical pickup 118 faces the optical disc D.

As shown in FIG. 14, the moving mechanism 112 includes a support member123 to support the optical pickup 111, a guide shaft 124 to support thesupport member 123 to be movable radially of the optical disc D, a guide125 to guide the support member 123 being moved, a sliding member 126 tocarry the support member 123, a coil spring 127 to force the slidingmember 126 axially of the guide shaft 124 in relation to the supportmember 123, a drive gear 128 to drive the sliding member 126, and adrive motor 129 to rotate the drive gear 128.

As shown in FIGS. 14 and 15, the support member 123 has the opticalpickup 111 mounted on the main surface thereof. It has also formedthereon a pair of holders 131 each having formed therein a through-holethrough which the guide shaft 124 is movably penetrated. The supportmember 123 further has a guide recess portion 132 slidably engaged onthe guide 125. The support member 123 has formed integrally at one endthereof a rack 133 which is movable in mesh with the drive gear 128.

The rack 133 is formed parallel to the axis of the guide shaft 124 asshown in FIG. 14. The rack 133 has a pair of engagement pieces 135engaged in the sliding member 126, and a retainer 136 to which the coilspring 127 is hooked at one end thereof.

As shown in FIG. 14, the guide shaft 124 is disposed across the opening116 formed in the base 113 with the axis thereof being parallel to theradius of the optical disc D. It is fixed at opposite ends thereof tothe base 113 with fixtures (not shown), respectively.

The guide 125 is formed from a resin material to have a linear shape asshown in FIG. 14. It is formed parallel to the axis of the guide shaft124 and along one lateral edge of the opening 116 in the base 113. Theguide 125 has slidably engaged thereon the guide recess portion 132 ofthe support member 123 as shown in FIG. 15.

As shown in FIG. 16, the sliding member 126 has a rack 138 formedthereon parallel to the axis of the guide shaft 124. The sliding member126 is installed with the rack 138 staggered about a half of one tooththickness in relation to the rack 133 of the support member 123. Thesliding member 126 has formed therein a pair of engagement holes 140 inwhich engagement pieces 135 formed on the rack 133 of the support member123 are engaged as shown in FIG. 14. Also, the sliding member 126 hasformed nearly in the center of the main surface thereof an opening 141in which the coil spring 127 is disposed. There is formed at one end ofthe opening 141 a retainer 142 on which the coil spring 127 is engagedat the other end thereof.

As shown in FIG. 14, the coil spring 127 is engaged at one end thereofon the retainer 136 provided on the rack 133 of the support member 123and at the other end on the retainer 142 provided on the sliding member126. The coil spring 127 forces, by its elasticity, the sliding member126 in the direction of arrow B₁ parallel to the axis of the guide shaft124 in relation to the rack 133 of the support member 123. Thus, thecoil spring 127 forces the rack 133 of the support member 123 and rack138 of the sliding member 126 to the drive gear 128 in a direction ofcanceling the backlash. That is, since the coil spring 127 forces theracks 133 and 138 with the rack 138 kept staggered about the half of onetooth thickness in relation to the rack 133 as mentioned above, so nobacklash will take place when the two racks 133 and 138 of the supportmember 123 and sliding member 126, respectively, are moved toward theouter- or inner-circumference side as driven by the drive gear 128 withwhich the racks are in mesh, so that the support member 123 and slidingmember 126 can be moved with a high accuracy.

As shown in FIG. 14, the optical pickup mechanism 110 has also a shuttermechanism 145 including a shutter 146 disposed movably to a maskingposition where it will mask the side of the objective lens 118 in theoptical pickup 111, opposite to the optical disc D, and to an unmaskingposition where it will unmask the objective lens 118. The shutter 146 isintended to prevent dust in an air flow inside the apparatus fromadhering to the face of the objective lens 118, opposite to the opticaldisc D, when the apparatus is in a waiting state for playing.

As shown in FIGS. 14 and 17, the shutter mechanism 145 includes theshutter 146 to mask the objective lens 118, a pivot 147 support theshutter 146 pivotably, and a tension coil spring 148 to force theshutter 146 to a position where it will unmask the objective lens 118.

As shown in FIG. 14, the shutter 146 consists of a shutter portion 151to mask the opening 121 in the cover 120 of the optical pickup 111, apivot support portion 152 to support the pivot 147 pivotably, a guideportion 153 engaged slidably on the cover 120 to guide the shutterportion 151, and an actuator portion 154 to pivot the shutter portion151 in the directions of arrows C₁ and C₂ in FIG. 14.

The shutter portion 151 is formed to have a generally plate-like shape,and slides above the cover 120 to mask or unmask the opening 121 in thecover 120. The pivot support portion 152 is formed integrally at one endof the shutter portion 151 and has formed therein a shaft hole in whichthe pivot 147 is pivotably inserted. The guide portion 153 is formed tohave a generally C-like section, and slidably engaged on a generallycircular guide piece 155 formed projected from and integrally with theperimeter of the cover 120. The actuator portion 154 is formed in aposition, on the pivot support portion 152, where it faces an actuatingprojection 156 provided on the base 113 as shown in FIG. 14. When theoptical pickup 111 is moved to the innermost circumference of therecording area, that is, to the lead-in area of the optical disc D, theactuator portion 154 abuts the actuating projection 156 to pivot thepivot support portion 152 about the axis of the pivot 147.

The pivot 147 is provided erected on the support member 123 andpivotably inserted in the pivot hole in the pivot support 152 of theshutter 146. As will be seen from FIG. 14, the tension coil spring 148is hooked at one end thereof to a retainer 158 provided on the supportmember 123 and at the other end to a retainer 159 formed on the pivotsupport portion 152 of the shutter 146.

Further, the moving mechanism 112 has a detection mechanism 161 todetect when the optical pickup 111 has moved to the lead-in area of theoptical disc D, as shown in FIG. 14. The detection mechanism 161 iscomposed of a detection or limit switch 162 to detect that the opticalpickup 111 is in a position for reading the lead-in area of the opticaldisc D, and a switch counterpart 164 to push a sense piece 163 of thedetection switch 162.

The detection switch 162 is installed to the support member 123 with thesense piece 163 directed orthogonally to the moving direction of theoptical pickup 111. Also, the switch counterpart 164 is formed projectedfrom and integrally with the base 113 to extend in the moving directionof the optical pickup 111. More specifically, when the optical pickup111 has moved nearly to the center of the lead-in area to read TOC ofthe optical disc D, the sense piece 163 of the detection switch 162 ispushed by the switch counterpart 164 and thus the detection switch 162detects that the optical pickup 111 is in the position for reading thelead-in area of the optical disc D.

As having previously been described with reference to FIG. 5, adetection signal produced by the detection switch 162 is supplied to themicrocomputer 61. Then, the microcomputer 61 will start counting apredetermined length of time by the timer 62. The drive motor 129 drivesthe support member 123 for the predetermined length of time to move theshutter 146 from the unmasking position to the masking position.

On the base 113, there is disposed a disc rotation drive mechanism torotate the optical disc D. The disc rotation drive mechanism is composedof a disc table 160 on which the optical disc D is set, and a spindlemotor (not shown) to rotate the disc table 160, as shown in FIG. 17.

In the optical pickup mechanism 110 constructed as above, when readinginformation from the optical disc D, the support member 123 is moved bythe moving mechanism 112 along the guide shaft 124 and guide 125 andthus the optical pickup 111 is moved radially of the optical disc D.

As shown in FIG. 17, in the optical pickup mechanism 110, when theoptical pickup 111 has been moved radially of the optical disc D to areading position generally in the center of the lead-in area of theoptical disc D, the actuator portion 154 of the shutter 146 abuts theactuating projection 156 on the base 113. At this time, the sense piece163 of the detection switch 162 is pushed by the switch counterpart 164provided on the base 113. Thus, the detection switch 162 supplies adetection signal to the microcomputer 61 which counts the predeterminedlength of time. The drive motor 129 continuously run for thepredetermined length of time to further move the optical pickup 111 overa predetermined distance as shown in FIG. 18. Thus, the shutter 146 ismoved in the direction of arrow C₂ against the force of the tension coilspring 148. In the optical pickup mechanism 110, when the optical pickup111 has been moved to the innermost circumference of the optical disc D,the shutter 146 is pivoted to the masking position where it will maskthe opening 121 in the cover 120, as shown in FIG. 18. Thus, it ispossible to prevent dust from adhering to the objective lens 118.

Note here that for a period after the detection switch 162 is turned onuntil the predetermined length of time elapses, namely, for a period forwhich the shutter 146 moves from the position where it masks theobjective lens 118 to the unmasking position, the microcomputer 61applies a reverse bias voltage to the focusing drive 64 as shown in FIG.6. Thus, the objective lens 118 moves the objective lens 118 to thefarthest position from the optical disc D and to the parking positioninside the cover 120 as shown in FIGS. 7 and 8. Thus, when the shutter146 is moved from the position where it unmasks the objective lens 118to the masking position, the shutter 146 can be prevented from touchingand scratching the objective lens 118. After elapse of the predeterminedlength of time, the microcomputer 61 applies no voltage or applies 0 Vto the focusing drive 64. Thus, the objective lens 118 returns from theparking position to the reference position as shown in FIGS. 7 and 8.Therefore, it is possible to prevent the shutter 146 from touching andscratching the objective lens 118. It should be noted that should theshutter 118 touch the shutter 146, the touch is just a point contact andthus the scratching of the objective lens 118 can be minimized.

In the optical pickup mechanism 110, when the optical pickup 111 hasbeen moved into the lead-in area located at the inner circumference ofthe recording area and where TOC is recorded, the shutter 146 is pivotedto the unmasking position and the objective lens 118 of the opticalpickup 111 will face the optical disc D, in which position the opticalpickup 111 is ready for reading information from the optical disc D. Asshown in FIG. 17, the optical pickup 111 will read information signalsfrom the optical disc D when the shutter 146 has been moved to theunmasking position.

In this case, when a read start signal is supplied to the microcomputer61, the detection switch 162 is on, whereby the microcomputer 61 willdetect that the shutter 146 of the optical pickup 111 is at the positionwhere it masks the objective lens 118. Simultaneously, the microcomputer61 applies a reverse bias voltage to the focusing drive 64 to move theobjective lens 118 from the reference position to the parking positionas shown in FIGS. 7 and 8 and thus prevent the shutter 146 from touchingthe objective lens 118 when the shutter 146 moves from the positionwhere it masks the objective lens 118 to the unmasking position. Themicrocomputer 61 counts the predetermined length of time by the timer62. When the microcomputer 61 detects that the predetermined length oftime has elapsed and the detection switch 162 is off, it will pull inthe objective lens 118 so that information signals, particularly, TOC,recorded in the lead-in area of the optical disc D can be read. That is,the focusing drive 64 is applied with a reverse bias voltage and a biasvoltage. Thus, the objective lens 118 is moved to the focusing controlposition, parking position and then to the in-focus position as shown inFIGS. 7 and 8. After that, the moving mechanism 112 is ready for readingthe information signals recorded in the optical disc D. The opticalpickup 111 is located nearly in the center of the lead-in area of theoptical disc D, and hence the optical pickup 111 can readily startreading TOC without having to make any operations for moving the opticalpickup 111.

The above operations for pulling in the objective lens 118 to theparking position by applying the focusing drive 64 with the reverse biasvoltage only at opening or closing of the shutter 151 are applicable ina following optical pickup device which is still another embodiment ofthe present invention.

Referring now to FIG. 19, there is illustrated in the form of anexploded perspective view the third embodiment of the optical pickupdevice according to the present invention. This optical pickup device ormechanism is generally indicated with a reference 201. As shown, theoptical pickup mechanism 201 includes an optical pickup 211 having anobjective lens 214, a moving mechanism 212 to move the optical pickup211 in the directions of arrows C₁ and C₂ parallel to the radius of theoptical disc D, and a base 213 to support the optical pickup 211 movablyand the moving mechanism 212.

As shown in FIG. 20, the optical pickup 211 is provided movably in anopening 216 formed in the base 213. The optical pickup 211 consists ofan optical system including an objective lens 214, a drive block to movethe objective lens 214 in a focusing direction parallel to the opticalaxis of the objective lens 214 and in a tracking direction orthogonal tothe optical axis, and a cover 218 to cover the drive block.

The drive block of the optical pickup 211 includes a lens holder to holdthe objective lens 214, a support mechanism to support the lens holdermovably, and an electromagnetic circuit to move the objective lens 214electromagnetically. Also, the optical system includes a light source toemit a laser light, a group of lenses forming together an optical path,and a photodetector to detect a return light from the optical disc D. Inthe optical pickup 211, a light beams emitted from a semiconductor laseror the like is collected by the objective lens 214 and projected ontothe signal recording surface of the optical disc D, and a return lightfrom the signal recording surface of the optical disc D is detected bythe photodetector. Thus, information signals recorded in the opticaldisc D are read. Also, when reading information signals recorded in theoptical disc D, the drive block moves the objective lens 214 in thefocusing and tracking directions for controlling the focusing andtracking of the objective lens 214.

The cover 218 is formed from a resin material such as ABS resin to havea generally box-like shape whose top is generally parallel to therecording surface of the optical disc D. The cover 218 has formedtherein nearly in the center thereof an operating 220 through which theobjective lens 214 can face the recording surface of the optical disc D,as shown in FIG. 19. The opening 220 is formed to have a generallyelliptic shape of which the longer diameter extends radially of theoptical disc D.

As shown in FIG. 19, the moving mechanism 212 includes a support member221 to support the optical pickup 211, a guide shaft 222 to support thesupport member 221 to be movable radially of the optical disc D, a guide223 to guide the support member 221 being moved, a sliding member 224 tocarry the support member 221, a coil spring 225 to force the slidingmember 224 axially of the guide shaft 222 in relation to the supportmember 221, a drive gear 226 to drive the sliding member 224, and adrive motor 228 to rotate the drive gear 226 by means of a gear train.

As shown in FIG. 20, the support member 221 has the optical pickup 211mounted on the main surface thereof. It includes a holder 231 throughwhich the guide shaft 222 is movably penetrated, and a pair of guidepieces 232 movably engaged on the guide 223. As shown in FIG. 20, thesupport member 221 has formed integrally at one end thereof a rack 233which is movable in mesh with the drive gear 226.

As shown in FIG. 20, the rack 233 is formed parallel to the axis of theguide shaft 222. The rack 233 has formed integrally thereon a pair ofengagement pieces 235 and 236 movably engaged in the sliding member 224and a retainer 237 to which the coil spring 225 is hooked at one endthereon. Also, a tooth 238 formed at the end, at the outer-circumferenceside of the optical disc D, of he rack 233 is formed generallytriangular to have a tooth thickness which is nearly a half of that ofother teeth 239 as shown in FIGS. 21 and 22 so that the rack 233 of thesupport member 221 is easily separated and disengaged from the drivegear 226.

As shown in FIG. 20, the support member 221 has formed at a positionthereof corresponding to the inner circumference of the optical disc Dan inner circumference-side stopper 241 which limits the support member221 from moving in the direction of arrow C₁. The innercircumference-side stopper 241 is formed projected from and integrallywith the support member 221 to extend parallel to the moving directionof the latter. Also, the base 213 is cut (indicated at a reference 242)in one lateral edge thereof at the inner circumference side of theopening 216. The inner circumference-side stopper 241 provided on thesupport member 221 comes into and abuts the inner end of the cut 242which will thus limit the support member 221 from moving toward theinner circumference of the optical disc D.

As shown in FIG. 20, the support member 221 has also formed at aposition thereof corresponding to the inner circumference of the opticaldisc D an outer-circumference stopper 243 which limits the supportmember 221 from moving in the direction of arrow C₂. Theouter-circumference stopper 243 is formed projected from and integrallywith the support member 221 to extend parallel to the moving directionof the latter. Also, the base 213 is cut (indicated at a reference 244)in the other lateral edge thereof at the outer-circumference side of theopening 216. The outer-circumference stopper 243 provided on the supportmember 221 comes into and abuts the inner end of the cut 244 which willthus limit the support member 221 from moving toward the outercircumference of the optical disc D.

As shown in FIG. 19, the guide shaft 222 is disposed across the opening216 in the base 213 and with the axis thereof being parallel to theradius of the optical disc D. It is fixed at opposite ends thereof tothe base 213.

As shown in FIGS. 19 and 20, the guide 223 is formed parallel to theaxis of the guide shaft 222 and along one lateral edge of the opening216 in the base 213. The guide 223 has movably engaged thereon the guidepieces 232 of the support member 221 to limit the freedom of the supportmember 221 moving about the axis of the guide shaft 222.

As shown in FIG. 19, the sliding member 224 has a rack 246 formedparallel to the axis of the guide shaft 222, and it is disposed on thesupport member 221 with the rack 246 placed flush with the rack 233 ofthe support member 221. The sliding member 224 has formed thereinengagement openings 248 and 249 in which the engagement pieces 235 and236 on the rack 233 of the support member 221 are engaged respectively,to be movable parallel to the axis of the guide shaft 222.

As shown in FIGS. 19 and 21, the sliding member 224 has formedintegrally thereon a pair of pins 250 which abut one (236) of theengagement pieces on the rack 233 of the support member 221 to limit theposition of the sliding member 224 in relation to the rack 233. Inaddition, the sliding member 224 has formed integrally thereon along therack 246 a guide piece 252 movably engaged with the drive gear 226, andalso has formed integrally thereon a retainer 253 to which the coilspring 225 is hooked.

The coil spring 225 is hooked at one end thereof to the retainer 237 onthe rack 233 of the support member 221 and at the other end the retainer253 on the sliding member 224 as shown in FIG. 19. Therefore, the coilspring 225 forces, with its own elasticity, the sliding member 224toward the rack 233 of the support member 221 and in the direction ofarrow C₂ parallel to the axis of the guide shaft 222.

As shown in FIG. 19, the drive gear 226 has a gear portion 255 which isin mesh with the racks 233 and 246 of the support member 211 and slidingmember 224, respectively. The drive gear 226 has also formed thereon ata portion near the free end thereof a guide groove 256 in which theguide piece 252 of the sliding member 224 is engaged movably, as shownin FIG. 19. The drive gear 226 and a gear train are rotatably disposedon the base 213 by means of the guide shaft 222. The drive motor 228 isdisposed on the base 213 and in mesh with the gear train.

As shown in FIG. 19, the moving mechanism 212 includes a shutter 258which is movable to a position where it will mask a side, opposite tothe optical disc D, of the objective lens 214 of the optical pickup 211and to a position where it will unmask the objective lens 214 and thelatter will thus face the optical disc D.

The shutter 258 is formed from a resin material such as POM(polyoxymethylene) to have a generally rectangular shape and an arealarge enough to cover the opening 220 in the cover 218, as shown in FIG.19. The shutter 258 is formed integrally with the sliding member 224with a pair of linear elastic connecting pieces 259 between them, asshown in FIG. 19. The connecting pieces 259 forces, by its elasticity,the shutter 258 to above the cover 218.

As shown in FIGS. 19 and 20, the moving mechanism 212 includes adetection mechanism 260 to detect when the optical pickup 211 has beenmoved to the inner-circumference side of the lead-in area of the opticaldisc D where TOC is recorded. The detection mechanism 260 includes asense piece 261 provided on the support member 221, and a detection orlimit switch 262 which detects when the sense piece 261 abuts thedetection switch 262 itself. The sense piece 261 is formed projectedfrom and integrally on a portion, near the bottom, of the support member221 to extend in the moving direction of the optical pickup 211. Thedetection switch 262 is disposed on a circuit board fixed to the base213 in a position where the sense piece 261 abuts the detection switch262 when the objective lens 214 of the optical pickup 211 has been movednearly to the radial center of the lead-in area of the optical disc D.When the optical pickup 211 has moved nearly to the radial center of thelead-in area of the optical disc D, the detection switch 262 is pressedby the sense piece 261 to produce a detection signal.

Note here that as having previously been described with reference toFIG. 5, the detection signal generated by the detection switch 262 issupplied to the microcomputer 61. Upon reception of the detection signalfrom the detection switch 262, the microcomputer 61 will start countinga predetermined length of time by the timer 62, and drive the drivemotor 228 for the predetermined length of time to move the slidingmember 224 over a predetermined distance to the rack 233 of the supportmember 221 and thus move the shutter 258 to the position where it willcover the opening 220 in the cover 218.

The optical pickup mechanism 201 constructed as above operates, as willbe described below, to cause the shutter 258 to mask or unmask theobjective lens 214 as the optical pickup 211.

First in a play waiting position of the optical pickup mechanism 201,the optical pickup 211 is positioned at the inner-circumference side ofthe lead-in area of the optical disc D. As shown in FIG. 23, the opening220 in the cover 218, that is, the objective lens 214, is masked by theshutter 258. Therefore, when in the play waiting position, the shutter258 prevents dust from adhering to the objective lens 214 in the opticalpickup mechanism 201. In the optical pickup mechanism 201, when in theplay waiting position, the rack 233 of the support member 221 isdisengaged from the drive gear 226 while the rack 246 of the slidingmember 224 having the drive gear 226 mounted thereon is in mesh with thedrive gear 226, as will be seen in FIG. 23.

Next, once the optical pickup mechanism 201 starts playing the opticaldisc D, as the sliding member 224 whose rack 246 is in mesh with thedrive gear 226 is moved by the drive gear 226 in the direction of arrowC₂, the shutter 258 is moved in the direction of arrow C₂ to theposition where it will unmask the opening 220 in the cover 218 and theobjective lens 214 will face the optical disc D, as shown in FIG. 24.Also, in the optical pickup mechanism 201, as the sliding member 224 ismoved in the direction of arrow C₂, the pins 250 on the sliding member224 abut the engagement piece 236 on the rack 233 of the support member221, as shown in FIG. 24.

In the optical pickup mechanism 201, when the pins 250 abut theengagement piece 236, the coil spring 225 forces, by its elasticity, thesupport member 221 in the direction of arrow C₂. Thus, in the opticalpickup mechanism 201, the rack 233 of the support member 221 is put inmesh with the drive gear 226 so that the teeth of the rack 233 of thesupport member 221 are aligned with those of the rack 246 of the slidingmember 224 and these teeth are put in mesh with the teeth of the drivegear 226, as shown in FIG. 25. At this time, the support member 221 isdisplaced a very short distance d in the direction of arrow C₂ owing tothe engagement of the rack 233 with the drive gear 226. Thus, in themoving pickup mechanism 212, as the support member 221 is displaced thedistance d in the direction of arrow C₂, the engagement piece 236 ismoved over the distance d away from the pins 250 as shown in FIG. 25. Aswill seen from FIG. 25, in the moving mechanism 212, as the engagementpin 236 thus moves away from the pins 250, the force or elasticity ofthe coil spring 225 will cancel the backlash between the racks 233 and246 of the support member 221 and sliding member 224, respectively, andthe drive gear.

As shown in FIG. 26, in the optical pickup mechanism 201, when readinginformation signals from the recording area of the optical disc D, theoptical pickup 211 is moved by the moving mechanism 212 with a highaccuracy in the directions of arrows C₁ and C₂ since the backlash iscanceled by the force of the coil spring 225. Thus, the informationsignals can accurately be read.

As shown in FIG. 24, in the optical pickup mechanism 201, when theoptical pickup 211 is further moved in the direction of arrow C₁, thestopper 241 provided on the support member 221 comes into and abuts theinner end of the cut 242 which will thus limit the support member 221from moving. At this time, the sense piece 261 of the support member 221abuts the detection switch 262 which will thus be turned on to detectthat the optical pickup has moved to the lead-in area. The detectionswitch 262 supplies a detection signal to the microcomputer 61. Themicrocomputer 61 will drives the drive motor 228 for the predeterminedlength of time counted by the timer 62. Thus, in the moving mechanism212, the support member 221 is limited from moving so that the tooth 238of the rack 233 of the support member 221 will leave from the drive gear226 and the rack 233 be disengaged from the drive gear 226, as shown inFIG. 24.

In the moving mechanism 201, since the support member 221 is limitedfrom moving, only the sliding member 224 is moved against the force ofthe coil spring 225 by the drive gear 226 drive for the predeterminedlength of time counted by the timer 62 in the direction of arrow C₁, asshown in FIGS. 23 and 24. Therefore, in the moving mechanism 212, thesliding member 224 is moved in the direction of C₁ in relation to thesupport member 221 to move the shutter 258 on the sliding member 224 inthe direction of arrow A₁, as shown in FIGS. 23 and 24. The shutter 258is thus moved to the position where it will mask the objective lens 214of the optical pickup 211.

Note here that for moving the shutter 258 to the masking position shownin FIG. 23 or to the unmasking position shown in FIG. 24, themicrocomputer 61 applies a reverse bias voltage to the focusing drive 64as shown in FIG. 6. Then the focusing drive 64 moves the objective lens214 to the parking position inside the cover 218 where it is farthestfrom the optical disc D, as shown in FIGS. 7 and 8. Thus, when theshutter 258 is moved to the unmasking position where it unmasks theobjective lens 214 or to the masking position, it is possible to preventthe shutter 258 from touching and scratching the objective lens 214.When the predetermined length of time has elapsed, the microcomputer 61applies no voltage, for example, 0 V, to the focusing drive 64. Thus,the objective lens 214 returns from the parking position to thereference position as shown in FIGS. 7 and 8. Therefore, it is possibleto prevent the shutter 258 from touching and scratching the objectivelens 214. It should be noted that should the objective lens 214 touchthe shutter 258 due to a vibration or the like, the touch is just apoint contact and so the scratch of the objective lens 214 can beminimized.

As having been described above, in the optical pickup mechanism 201according to the present invention, when the objective lens 214 of theoptical pickup 211 is in the lead-in area, the shutter 258 is positivelyplaced in the unmasking position and so the optical pickup 211 canaccurately read the lead-in area.

In this optical pickup mechanism 201, the opening 220 in the cover 218can positively closed by the shutter 258 to prevent dust from adheringto the objective lens 214.

Note that the optical disc D referred to in the above description of theembodiments is a one having recorded therein information signals ofwhich reading is started at the inner-circumference area of the opticaldisc D but the present invention is applicable to an optical disc havingrecorded therein information signals of which reading is started at theouter-circumference area of the optical disc. Also, the initialposition, namely, play start position, of the optical pickup may be atthe inner- or outer-circumference side of the optical disc. Further, themoving mechanism may be designed for the shutter to mask or unmask theobjective lens when the optical pickup has moved to theouter-circumference position. Namely, the moving mechanism may bedesigned such that when the optical pickup is at the outer-circumferenceposition, the shutter will mask or unmask the objective lens and thuswhen the shutter is moved for masking or unmasking, the objective lenswill be moved from the reference position to the parking position whereit is moved away from the optical disc.

Also note that the aforementioned disc drive unit is designed to readinformation signals from the optical disc but it may be designed torecord information signals to a recordable optical disc or rewritableoptical disc. Also, a magnetic head mechanism may be provided in aposition where it faces the optical pickup device for writing andreading information signals to and from any other optical disc such as amagneto-optical disc.

INDUSTRIAL APPLICABILITY

As having been described in the foregoing, by moving a shutter by a feedscrew which moves the optical pickup radially of an optical disc in sucha manner as to mask or unmask the objective lens, the present inventionprovides an optical disc drive unit designed smaller and simpler inconstruction and in which any foreign matter such as dust can beprevented from adhering to he objective lens, without having to provide,as in the conventional disc drive units, any compartment to house theoptical pickup when the apparatus is not in use as a mechanism toprevent any foreign matter such as dust from adhering to the objectivelens.

Further, the present invention can prevent the shutter from touching andscratching or otherwise damaging the objective lens since the objectivelens is further moved from a predetermined position away from theoptical disc when masking the objective lens by the shutter.

1. A recorder and/or player, comprising: an optical pickup having anobjective lens supported movably along a substantially linear guideprovided parallel to a radius of an optical disc; and a moving mechanismincluding: a feed screw provided substantially parallel to the radius ofthe optical disc; and a sliding member engaged at one end thereof on thefeed screw, having formed at an other end a shutter that masks theobjective lens, and being held on the optical pickup with an elasticmaterial placed therebetween; the optical pickup being moved along withthe sliding member as the sliding member is moved radially of theoptical disc by the feed screw in rotation; when the optical pickup hasmoved along with the sliding member in one direction and arrived at apredetermined position, the optical pickup is limited from moving, andas the feed screw is further rotated, only the sliding member is movedin the one direction against the force of the elastic member, so thatthe shutter of the sliding member masks the objective lens; a detectionswitch provided on one of the base or the optical pickup to detect whenthe optical pickup has arrived at the predetermined position at theinner-circumference side of the optical disc and a switch counterpartprovided on an other side of the optical disc; and a focusing controllerto control focusing of the objective lense in relation to the opticaldisc, wherein when the optical pickup has moved along with the slidingmember in the one direction and arrived at the predetermined position,the detection switch is turned on by the switch counterpart and areversed voltage of a voltage applied for the focusing control isapplied to the focusing controller, so that the focusing controllermoves the objective lens along the optical axis thereof from apredetermined lens position to a lens position further away from theoptical disc; and when the feed screw is further rotated for apredetermined length of time with the objective lens having been movedto the lens position further away from the optical disc, as the opticalpickup is limited from moving, and only the sliding member is moved inthe one direction against the force of the elastic member, the shutterof the sliding member masks the objective lens.
 2. The recorder and/orplayer as set forth in claim 1, further comprising: a limiter providedon a rotation drive provided on a base having the guide formed thereon,wherein the rotation drive drives the optical disk; and a stopperprovided in a position on the optical pickup opposite to the limiter;the optical pickup being moved along with the sliding member as thesliding member is moved toward the inner-circumference side of theoptical disc by the feed screw in rotation; and when the optical pickuphas moved along with the sliding member in the one direction until thestopper abuts the limiter, the optical pickup is limited from moving,and as the feed screw is further rotated, only the sliding member ismoved in the one direction against the force of the elastic member, sothat the shutter of the sliding member masks the objective lens.